LOS ANGELES, June 2 (Reuters) - The California Senate voted on Tuesday to allow unauthorized immigrants to buy health insurance on a state exchange created under the U.S. Affordable Care Act, a measure that would make the state the first to offer that kind of coverage.

The bill would not provide a subsidy for undocumented immigrants to buy health insurance, unlike U.S. citizens and legal residents who can qualify for such assistance based on their incomes, said Jesse Melgar, a spokesman for the bill's author, Senator Ricardo Lara.

The Senate voted 28-11 in favor of the proposal, which still must be approved by the state Assembly and signed by the governor, Melgar said. Additionally, a federal waiver would be required for California to implement the measure.

"Today's vote is a transformational and decisive step forward on the path to achieving health for all," Lara, a Democrat, said in a statement.

Undocumented immigrants in the United States can already buy private health insurance outside the exchanges.

But the bill would allow the hundreds of thousands of families in California with a mix of U.S. citizens and undocumented immigrants to sign up at the exchange together as a family, said Anthony Wright, executive director of consumer advocacy group Health Access.

"So maybe the grandmother or the father won't get a subsidy but they could all be signed up in the same plan, even if they have different levels of premiums," he said.

The bill would also allow people 18 or younger living in California without legal immigration status to sign up for Medi-Cal, the state's healthcare program for low-income people, Melgar said.

Furthermore, it would allow older unauthorized immigrants who cannot afford to buy insurance to sign up for coverage, but a state allocation to fund that would have to be made later.

"It's just one additional step that the California legislature is trying to take to eliminate any legal distinction between illegal aliens and legal residents of California," said Ira Mehlman, spokesman for the Federation for American Immigration Reform, which calls for restrictions on immigration.

About 7 percent of California's population, or 2.6 million people, lack legal immigration status. In 2012, the state spent over $600 million on emergency room and other health-related services for people living in the state illegally. (Reporting by Alex Dobuzinskis; Editing by Cynthia Johnston and Mohammad Zargham)